1. Field of the Invention
This invention relates to a redundant blower unit used to cool underlying heat emitting electrical elements such as a bank of CPU cards. The blower unit contains four blowers, two at a lower elevation and the other two at a higher elevation. The space between the bottoms of the blowers and the bottom of the unit constitutes a plenum which allows air drawn into the unit to circulate and expand from a straight line exit from the unit below. Each blower discharges into an individual exhaust duct, the ducts discharging horizontally sideward. If one blower fails, its exhaust duct becomes an air inlet. Arranging the blowers at different levels ensures that the air drawn through the duct of the failed blower will be blown out of the unit through the other blower at the same level as the failed blower. This enables the other two blowers at the other level to operate efficiently.
2. Description of Related Art
Blower units of substantially the same dimensions as the unit of the present invention have been used for similar purposes. However these units employ a single, large blower. When the large blower fails, the underlying electrical units overheat and may be considerably damaged. Other blower units have used multiple blowers but not arranged in tiers, as in the present invention. By using four separate blowers, the redundancy greatly reduces the likelihood of damage to the electrical elements being protected. When the air cooling means providing ventilation for devices which require such cooling fail, the device will fail. Hence it is desirable in such installations as computers to have a fail tolerant system. The present invention provides redundant blowers so that even with failure of one blower, there is adequate cooling.
The present invention employs four individual backward curved motorized impellers, all of which run simultaneously under normal operating conditions and are more than adequate to supply cooling to the computing unit which is located below the blower unit. A stopped or seized impeller or a burned out motor does not result in inadequate cooling because of the redundancy of the blowers.
The impellers are placed within the unit in such locations that there is little or no change in the ability of the redundant blowers to supply adequate cooling to the system regardless of which of the four impellers has actually failed.
The foregoing results are achieved by placing two blowers on each of two tiers. In normal operation with all four blowers functioning, hot air from the underlying heat emitting unit rises into a plenum at the bottom of the blower unit and then through each of the four blowers. The blowers discharge into individual ducts which direct the exhaust air horizontally sidewardly to the exterior.
If one blower fails, its exhaust duct becomes an air inlet. Since air takes the path of least resistance, air inletting through the failed blower duct flows into the blower at the same level (i.e., in the same tier) as the failed blower, mixing with some of the hot air emitted from the underlying unit. The bulk of the hot air goes through the two blowers in the other tier.
Failure of a blower is sensed by a tachometer sensor on its motor. A controller interprets the signals and provides a warning to the operator that one of the blowers has failed.